Roll paper often used in a printer may skew when the roll paper is drawn out. Therefore, in the past, the printer that uses the roll paper regulates the movement of end faces of the roll paper to prevent the skew of the roll paper.
JP-A-2007-161456 discloses, as an example of the prevention of the skew of the roll paper, skew correcting means for pressing a side of the roll paper in a width direction of the roll paper. The skew correcting means presses a winding outer pressing member having a flat surface against the side of the roll paper using two skew correcting springs (see paragraphs 0062 to 0063 and FIG. 12).
Another example of the prevention of the skew of the roll paper is a method of using a label fastener 901 shown in FIG. 14. The label fastener 901 is a bent metal bar and has a U-shaped contact section 904 that comes into contact with an end face of the roll paper and inserting sections 905 that project in an orthogonal direction with respect to the contact section 904. A support shaft 902 for the roll paper has, on an outer circumferential surface thereof, a pair of grooves 903 extending in an axis direction. After inserting the roll paper over the support shaft 902, the label fastener 901 is set by fitting the inserting sections 905 in the grooves 903 of the support shaft 902 and pushing in the inserting sections 905. When the label fastener 901 is set, since the contact section 904 comes into contact with the end face of the roll paper, the label fastener 901 can regulate the movement in the width direction of the roll paper.
In the skew correcting means disclosed in JP-A-2007-161456, a movable range of the outer pressing member depends on a stroke of the skew correcting springs. Therefore, it is difficult for the skew correcting means to cope with plural kinds of roll paper having different widths.
In the label fastener 901 shown in FIG. 14, it is difficult to set tightening force of the inserting sections 905 applied to the support shaft 902. Specifically, when the tightening force of the inserting sections 905 applied to the support shaft 902 is too strong, it is difficult to attach the label fattener 901 to and detach the label fastener 901 from the support shaft 902. In this case, if an operator strongly pushes in the label fastener 901, this likely causes a rotation failure of the roll paper. Conversely, if the tightening force of the inserting sections 905 applied to the support shaft 902 is too weak, the label fastener 901 is pushed by the roll paper, which is about to move in the width direction, and moves.